Anchoring device for a floating buoy

ABSTRACT

The invention relates to an anchoring means for connecting a buoy with a fixed point below the water surface, which anchoring means contains at least over part of its length an elongated elastic member that can be elongated over 100 percent and consists of natural rubber mixed with polybutadiene and/or a plasticizer, and is able to withstand at least 30,000 elongations of more than 100 percent without tearing or breaking. The anchorage means according to the invention enables the use of smaller buoys that nevertheless are not submerged by current and waves.

United States Patent Coruells M. Verhagen Inventor Heemstede, Netherlands Appl. No. 801,849 Filed Feb. 24, 1969 Patented July 6, 1971 Assignee Datawell N.V.

llaarlem, Netherlands Priority Mar. 1, 1968 Netherlands 6,803,005

ANCHORING DEVICE FOR A FLOATING BUOY 3 Claims, 2 Drawing Figs.

[1.8. CI. 9/8, 174/9, 174/69, 174/70 lnt.Cl ..B63b 21/52, 1101b l/0O,1-10lb 7/06 Field of Search 1. 174/9, 9.5,

[56] References Cited UNITED STATES PATENTS 3,101,491 8/1963 Salo 9/8 3,419,702 12/1968 Piel 174/9 (.5) X 3,423,777 1/1969 Feyling 9/8 FOREIGN PATENTS 1,285 1859 Great Britain 174/9 (.5)

Primary Examiner Laramie E. Askin Attorney-Brumbaugh, Graves, Donohue and Raymond ABSTRACT: The invention relates to an anchoring means for connecting a buoy with a fixed point below the water surface, which anchoring means contains at least over part ofits length an elongated elastic member that can be elongated over 100 percent and consists of natural rubber mixed with polybutadiene and/or a plasticizer, and is able to withstand at least 30,000 elongations of more than 100 percent without tearing or breaking. The anchorage means according to the invention enables the use of smaller buoys that nevertheless are not submerged by current and waves.

cououcnvs FLUID PATENTEI] JUL 6L9?! 3,590 40 FIG.

CONDUCTIVE FLUID v VIII/[III] F/GZ INVENTOR. CORNELIS M. VERHAGEN his ATTORNEYS ANCHORING DEVICE FOR A FLOATING BUOY The invention relates to an anchoring device for a floating buoy in shallow streaming water.

The invention relates likewise to a floating buoyanchored by such a device.

With the anchoring of floating buoys, especially in shallow streaming water, difficulties arise because of the fact, that, when the buoy is carried along with the stream, the anchoring cable is tightly stretched. in this position a wave with not too small a height may first untighten the cable and after this tighten it again, by which a tug is generated at the moment that the cable is stretched. When the cable is tightly stretched there is the risk, that the high waves flow over the buoy, such that it comes below the water surface. This being acceptable, although not desirable, for beaconing purposes it is unacceptablein other cases, e.g. for measuring buoys. In the first place the tug to the buoy will disturb instruments in the buoy, the working of which may be based on inertia, while in the second place measuring buoys with transmitter apparatus cannot transmit when being submerged. The last and most important disadvantage is connected with buoys measuring the height of waves, because of the fact that, when the buoy is submerged, the relation with the surface is lost and wrong values are measured.

A further disadvantage of the tug is that it forms a heavy loading for the cable and the anchorage, so that these have to be constructed heavily.

For a small buoy the danger that it is submerged is considerably greater than for a big one, because the floating capacity of the buoy is proportional with its volume and the drag-along forces, being exerted by the water upon the buoy, are in principle proportional with the sectionalarea of the buoy. As compared with beaconing buoys most of the measuring buoys only need a small volume. In consequence it is very important to look for an anchorage which effectively opposes the submerging of relatively small buoys, because then the use of small buoys is acceptable.

For mooring ships the use of elastic mooring cables has already been proposed. According to another proposal for mooring ships use is made of a combination of a somewhat elastic and a nonelastic cable. With these proposals the problem how to prevent a buoy, which is anchored to a point below the water surface, from being submerged, does not play any part. Moreover it is important with buoys that the anchorage is capable to withstand long lasting pulling forces, with which the anchoring cable is extremely stretched, without causing creep of the cable. With the proposed moorings of ships also these problems only play a secondary part.

With the anchoring of buoys in shallow water, to which the invention relates, it is already proposed to install an auxiliary float below the water surface. This auxiliary float, however, makes a movement such that the tightly or nearly tightly stretching of the connection between the mooring point, the auxiliary float and the floating buoy, cannot be prevented always, so that the mooring is not improved much regarding the dangers of generating tugs and the submerging of the buoy.

Also it has already been proposed to let float one or more auxiliary floats on the water surface and to have this or these connected with the buoy at the one side and with a fixed anchoring point at the other side. With this an improvement is obtained regarding the possibility of the buoy being submerged, but a horizontal portion of a cable near the water surface mostly is not acceptable, especially not in the neighborhood of shipping. In this connection it is important to point out that'the position of the buoy in view of the anchoring point is dependent on the direction of the currents, which in many cases is varying.

The invention solves the above mentioned difficulties and provides an anchorage for a floating buoy with which also when it is anchored in streaming, shallow water and when high waves can occur, there is no danger that the buoy is submerged. According to the invention this is obtained by the fact that the anchoring means, for at least part of its length, consists of an elastic material with a relative elongation of at least percent.

In applying the invention a drawback force is continuously present, opposite to the horizontal force component which is exerted by the water to the buoy, the connecting means under all circumstancesremaining so elastically, that no tug can occur. lf now the movement of the water particles of a wave is in the current direction so that the relative movement of the water particles in view of the anchoring point is maximal, the connecting means will be stretched and will shrink again in that period of the wave movement, during which the movement of the water particles is contrary to the current direction. By this with each wave the buoy comes back so far that it can follow the horizontal and vertical components of movement of the succeeding wave without difficulties.

The materials which can be used according to the invention can be indicated as to be rubberlike materials, with an admissible relative elongation of at least 100 percent. The elongation is that elongation which may occur without rupturing the material. With this it has to be thought of the fact that with anchoring buoys the elongation is continuously variable, so that the admissible elongation is that with which also no fatigue breakdown occurs. Dependent on the storminess of the area in which the buoy lies, in practice a resistance against 30,000 up to 100,000 elongations, while maintaining an induced stress between the elongations, will be amply sufficient.

ln opposing fatigue breakdown it is important that the specific stress in the material is maintained low. When there is started from an acceptable elongation of 100 percent, the specific stress, however, increases with the modulus of elasticity.

According to a further elaboration of the invention it is provided that the modulus of elasticity of the material is smaller than 25 kg./cm.". In practice rubberlike materials have been found with a modulus of elasticity between 3 and 25 kg./cm. at 100 percent elongation and an advisable elongation of at least 100 percent without the possibility of fatigue breakdown. These materials are natural and artificial rubbers.

With the anchorage of buoys the ratio between the length of the connecting means and the height of the waves which can be expected plays a part. Now the length of the anchoring means highly depends on the depth. The maximum wave height increases only very little with depths of more than 15 m., so that with increasing depths the ratio between the wave height and the length of the connecting means becomes gradually favorable.'With a depth of 1000 n. the wave height is so small in view of the mooring cable, that an elongation of the anchoring cable equaling 0.5 percent of the length of the cable is sufficient. Nonrubberlike materials are known which can easily stand such an elongation without any chance of fatigue breakdown, so that in this case the invention hardly yields any profit. When, however, the depth decreases so that the wave height forms a larger percentage of the length of the connecting means, the advantages of the invention come forward.

When a buoy with a volume of l0 m. and a loading without the anchoring of 60' percent (which means that without the anchoring 4 m. of the buoy is protruding above the water) is anchored in shallow water (17 m.) by means of a chain as anchoring means, this buoy is still submerged even in case of moderate circumstances, such as an average velocity of 1.2 m./sec. and waves with a height of about 7 m., measured between wave top and trough. With extreme conditions, e.g. a current velocity of 2 m./sec. and a wave height of 12 m., a buoy with the same relative loading of 60 percent must have a volume of over 250 m. for not being submerged.

In applying the invention, however, under the same conditions it is possible by using the anchorage according to the invention to have a buoy, with a volume of 0.16 m. and a loading without the anchorage of 60 percent, not submerged, in

case of a current velocity of 2 m./sec. and wave heights of 14 m.

The rubberlike material being employed may not show much creep in case of possible low temperatures (in practice to about C.). Large creep (150 up to 250 percent of the original length) especially occurs with pure natural rubbers, mainly in consequence of the so-called crystallization. Pure polybutadiene rubbers indeed do not show crystallization, but have a small tear strength. Adding styrene and carbon-black to polybutadiene rubbers (SBR) gives a far better tear strength, but in that case fatigue breakdown may occur already relatively quick with low stresses.

A suitable rubber for applying with the invention appears to be a natural rubber filled with carbon-black and mixed with polybutadiene and/or plasticizer.

The elastic portion of the connecting means may have nearly any sectional shape. For manufacturing-technical reasons, generally speaking, a solid execution will be preferred, but it will be obvious that also other shapes can be applied, e.g. thick walled tubes. For counterbalancing the floating power of such a tube and to protect it from being crushed, it can be filled with a liquid. When this liquid is electrical conducting and at the outer ends of the tube electrodes are provided which are in contact with this liquid, a reliable electrical connection may be obtained. A

Another possible embodiment of the elastic connecting means is that it is a cable of rubberlike material, which is formed from a number of cords. The advantage of this is that a possible rupture by tearing is limited to one cord of the cable.

Because the elastic part of the connecting means according to the invention has an acceptable elongation of at least 100 percent, generally speaking a given length of this part will suffice, this length being about equal to the maximum wave height which can be expected. As this does not increase with increasing depth of the water, the further connecting means may be executed as little or not elastic, such as a cord of steel or plastic.

The invention also relates to an anchoring means as described above.

Other objects and advantages of the present invention will become apparent from the ensuing description of the preferred embodiment of the invention, reference being had to the accompanying drawings in which:

FIG. 1 is a perspective view of one embodiment of the anchoring device for a floating buoy.

FIG. 2 is a cross-sectional view of the connection between the cable which is attached to a fixed anchoring device and the rubber tube which is attached to a buoy.

Referring to FIG. 1, the anchoring device is submerged in a stream and is attachable to a buoy generally designated by the numeral 1. Connected to buoy l at its submerged portion is a rubber tube 2 which, as mentioned above, is preferably hollow and formed of a natural rubber mixed with polybutadiene and/or a plasticizer and has an acceptable elongation of at least I00 percent.

As best illustrated in FIG. 2, rubber tube 2 can be filled with a liquid 3, which is. preferably of the electrical conducting variety. Cable 4 at one end is connected to rubber tube 2 at connecting point 5 and may be clamped thereto by any suitable clamping means. .The other end of cable 4 is connected to fixed anchor 6 for maintaining buoy l in a generally fixed location in the stream.

As best illustrated in FIG. 2, connecting point 5 includes an electrode 7, one end of which is in contact with conductive liquid 3 for providing a reliable electrical connection with electrical instruments contained in buoy 1.

The lower end of rubber tube 2 fits in telescopic relation over the terminal end of cable 4 and may be clamped thereto by any suitable clamping means to form a liquid-tight connection.

I claim:

1. An anchoring device for a floating measuring buoy in which an elongated flexible connecting member connects the buoy with a fixed point below the water surface, character zed in that at least part of the length of the connecting member consists of an elastic material with a relative elongation of at least percent and is formed as a tube of rubberlike material which is filled with an electrically conducting liquid, and electrodes provided near the ends of the tube, which electrodes are in contact with the said liquid.

2. Anchoring device according to claim 1, characterized in that the rubberlike material is a natural rubber compound to which polybutadiene has been added.

3. Anchoring device according to claim 1, characterized in that the rubberlike material is a natural rubber compound to which polybutadiene plus plasticizer has been added.

P0-1050 UNITED STATES PATENT OFFICE 5 9 CERTIFICATE OF CORRECTION Patent No. 3 59 L408 Dated y 6 97 Inventor) Cornelis M. Verhagen It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 10, change "advisable" to admissible Signed and sealed this l th day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

1. An anchoring device for a floating measuring buoy in which an elongated flexible connecting member connects the buoy with a fixed point below the water surface, characterized in that at least part of the length of the connecting member consists of an elastic material with a relative elongation of at least 100 percent and is formed as a tube of rubberlike material which is filled with an electrically conducting liquid, and electrodes provided near the ends of the tube, which electrodes are in contact with the said liquid.
 2. Anchoring device according to claim 1, characterized in that the rubberlike material is a natural rubber compound to which polybutadiene has been added.
 3. Anchoring device according to claim 1, characterized in that the rubberlike material is a natural rubber compound to which polybutadiene plus plasticizer has been added. 